of growing concerns that some of the damage from repeated concussions doesn't go away, one leading boston researcher proposed very tough guidelines for the youngest athletes. >> we believe that kids under the age of 14 shouldn't play collision sports as they're currently being played. >> and dr. kent recommends no full body checking under age 14 in ice hockey and for soccer players, not letting the younger kids head the ball. >> the young child is particularly vulnerable to brain injury. >> at the pro level, greater recognition of the long-term effects of brain trauma prompted the nfl to enact new rules on concussion that is dictate when players can get back on the field. the nfl players' association even formed a traumatic brain injury committee of which dr. jim eckland is part. >> and a numb things to help -- number of thinks to help protect the players as that game's gotten faster and more -- more aggressive and the athletes have gotten more powerful. >> he says making tackle football off-limits at the youth or pop warner level seems a bit rigid but young athletes need to be taught how